Many vehicles include an automatic transmission. Generally, an automatic transmission automatically upshifts or downshifts based upon a particular transmission schedule and vehicle load. When a vehicle enters an uphill or downhill slope, the load on the engine may increase or decrease, respectively, as the effects of gravity act on the vehicle. Accordingly, in some situations, it may be advantageous for a vehicle to shift gears depending on the grade of the terrain on which the vehicle is driving.